Electric submersible pump variable speed drive controller

ABSTRACT

An electric submersible pump (ESP) variable speed drive (VSD) controller is described. A VSD control system includes a pump assembly including an induction motor operatively coupled to a pump, a power cable and a transformer electrically coupled between the induction motor and a VSD controller that controls a speed of the induction motor, the VSD controller including a converter section that sends a direct current (DC), a DC link including a DC smoothing capacitor that smooths the DC, an inverter that converts the smoothed DC to a pulse width modulated (PWM) output voltage, the inverter including at least one silicon carbide (SiC) power semiconductor module, and a PWM filter that filters the PWM output voltage to produce near sinusoidal voltages, the PWM filter including inductors, and the PWM filter sending voltage to the transformer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.15/493,490 to Yohanan et al., filed Apr. 21, 2017 and entitled ELECTRICSUBMERSIBLE PUMP VARIABLE SPEED DRIVE CONTROLLER, which claims thebenefit of U.S. Provisional Application No. 62/325,897 to Yohanan etal., filed Apr. 21, 2016 and entitled “ELECTRIC SUBMERSIBLE PUMP POWERSYSTEM,” each of which are hereby incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Embodiments of the invention described herein pertain to the field ofelectric submersible pump (ESP) assemblies. More particularly, but notby way of limitation, one or more embodiments of the invention enable anESP variable speed drive controller.

2. Description of the Related Art

Submersible pump assemblies are used to artificially lift fluid fromunderground formations, such as oil, natural gas and/or water wells, tothe surface. These wells are typically thousands of feet deep, with thepump assembly placed inside the deep well. A typical electricsubmersible pump (ESP) assembly consists, from bottom to top, of anelectric motor, seal section, pump intake and centrifugal pump, whichare all connected together with shafts. The electric motor suppliestorque to the shafts, which provides power to the centrifugal pump. Theelectric motor is generally a two-pole, three-phase, squirrel cageinduction design connected by a power cable to a power source located atthe surface of the well. The power cable includes a motor lead assemblyand downhole cable, and extends from the downhole motor deep within thewell, to a transformer connected to a power generating system at thesurface of the well. These ESP power cables are typically between about4,000 to 12,000 feet in length, depending on well depth, since the cablemust extend from deep within the well to the surface where the powersource is located.

The ESP power generating system typically includes a variable speeddrive (VSD) that is connected to an electrical grid. The VSD is locatedat the surface of a well that employs the ESP assembly. The VSD, alsosometimes called a variable-frequency drive, adjustable frequency drive,AC drive, micro drive or inverter drive, is an adjustable speed driveused to control the speed and torque of the ESP induction motor byvarying motor input frequency and voltage. A VSD system may comprisethree main sub-systems: the AC motor that is the ESP three-phaseinduction motor, the main drive controller assembly and the driveuser-interface. The controller is commonly a solid-state powerelectronics conversion system. An embedded microprocessor control systemsuch as a VSD controller is generally implemented as firmware and maygovern the overall operation of the VSD.

The VSD solid-state power electronics conversion system for ESPassemblies typically consists of four distinct subsystems: a convertersection, a direct current (DC) link, an inverter section and a pulsewidth modulated (PWM) filter. The typical converter section consists ofa three-phase, six-pulse, full-wave diode bridge. The DC link consistsof a capacitor which smooths out the converter's DC output ripple andprovides a stiff input to the inverter. This filtered DC voltage isconverted to PWM output voltage using the inverter's active switchingelements. These PWM signals are filtered by the PWM filter section toobtain near sinusoidal voltages. PWM filters currently require largesteel inductors. Current inverter sections operate at low switchingfrequencies, and the lower the frequency, the more steel is required forthe inductor. Large steel inductors are the primary contributor to thelarge footprint of conventional VSD controllers.

Current implementation of the inverter section is realized using silicon(Si) power semiconductor devices. However, silicon power semiconductordevices are limited in their operating temperatures, current density andblocking voltages. These limitations lead to operational inefficienciesin conventional VSDs operating ESP motors, such as high switchinglosses, in addition to the aforementioned large footprints. Aconventional VSD with a Si power semiconductor device is only 97%efficient without a PWM filter. Thus, up to three-percent of power sentto the VSD controller dissipates and is and not available to the ESPmotor. Three-percent dissipation represents a significant loss in a 500kVA drive. There is an inverse relationship between switching frequencyand the footprint of the magnetics.

High switching losses and large footprints are particularly problematicin offshore ESP applications. In offshore applications, the VSDcontroller must fit on a floating unit where space is at a premium andmust be used efficiently in order to lift and collect hydrocarbons inthe middle of the ocean.

As is apparent from the above, current VSD controllers undesirably limitoperation of ESP assemblies. Therefore, there is a need for an improvedESP VSD controller.

BRIEF SUMMARY OF THE INVENTION

One or more embodiments of the invention enable an electric submersiblepump (ESP) variable speed drive (VSD) controller.

An ESP VSD controller is described. An illustrative embodiment of anelectric submersible pump (ESP) variable speed drive (VSD) controlsystem includes an ESP assembly including a two-pole, three-phasesquirrel cage induction motor operatively coupled to a multi-stagecentrifugal pump, an ESP power cable and a transformer electricallycoupled between the two-pole, three-phase squirrel cage induction motorand a VSD controller, the VSD controller controlling a speed of thetwo-pole, three-phase squirrel cage induction motor, the VSD controllerincluding a converter section that sends a direct current, a DC linkincluding a DC smoothing capacitor that smooths the direct current, aninverter active switch section that converts the smoothed direct currentto a pulse width modulated (PWM) output voltage, the inverter activeswitch section including at least one silicon carbide (SiC) powersemiconductor module, each of the at least one SiC power semiconductormodules including a pair of SiC MOSFETs, wherein a first SiC MOSFET ofthe pair of SiC MOSFETs is electrically connected to a second SiC MOSFETof the pair of SiC MOSFETs by a terminal, the terminal serving as adrain of the first SiC MOSFET and a source of the second MOSFET, avoltage switch, and a feedback line, a PWM filter that filters the PWMoutput voltage to produce near sinusoidal voltages, the PWM filterincluding a plurality of inductors, and the PWM filter sending voltageto the transformer. In some embodiments, the converter section includesa three-phase, six-pulse, full-wave diode bridge. In certainembodiments, the VSD controller includes an LCL input filter and theconverter section includes an active front end, the active front endincluding a second at least one SiC power semiconductor module, each ofthe second at least one SiC power semiconductor modules including asecond pair of SiC MOSFETs, wherein a first SiC MOSFET of the secondpair of SiC MOSFETs is electrically connected to a second SiC MOSFET ofthe second pair of SiC MOSFETs by a second terminal, the second terminalserving as a drain of the first SiC MOSFET of the second pair of SiCMOSFETs and a source of the second MOSFET of the second pair of SiCMOSFETs, a second voltage switch, and a second feedback line. In someembodiments, the ESP VSD control system further including an offshoreplatform above a well, wherein the ESP assembly is downhole in the well,the VSD controller is on the offshore platform, and wherein the ESPpower cable extends between the VSD controller and the ESP assembly. Incertain embodiments, the inverter active switch section includes threeSiC power semiconductor modules, each module packaged in a housing andincluding a heat sink baseplate. In some embodiments, each of the atleast one SiC power semiconductor modules includes a plurality of thepairs of SiC MOSFETs.

An illustrative embodiment of an electric submersible pump (ESP)variable speed drive (VSD) control system includes an ESP assemblyincluding a two-pole, three-phase squirrel cage induction motoroperatively coupled to a multi-stage centrifugal pump, an ESP powercable and a transformer electrically coupled between the two-pole,three-phase squirrel cage induction motor and a VSD controller, the VSDcontroller controlling a speed of the two-pole, three-phase squirrelcage induction motor, the VSD controller including a converter sectionthat sends a direct current, a DC link including a DC smoothingcapacitor that smooths the direct current, an inverter active switchsection that converts the smoothed direct current to a pulse widthmodulated (PWM) output voltage, the inverter active switch sectionincluding at least one silicon carbide (SiC) power semiconductor module,each of the at least one SiC power semiconductor modules including apair of SiC IGBT devices, wherein a first SiC IGBT device of the pair ofSiC IGBT devices is electrically connected to a second SiC IGBT deviceof the pair of SiC IGBT devices by a terminal, the terminal serving as adrain of the first SiC IGBT device and a source of the second IGBTdevice, a voltage switch, and a feedback line, a PWM filter that filtersthe PWM output voltage to produce near sinusoidal voltages, the PWMfilter including a plurality of inductors, and the PWM filter sendingvoltage to the transformer. In some embodiments, the converter sectionincludes a three-phase, six-pulse, full-wave diode bridge. In certainembodiments, the VSD controller includes an LCL input filter and theconverter section includes an active front end, the active front endincluding a second at least one SiC power semiconductor module, each ofthe second at least one SiC power semiconductor modules including asecond pair of SiC IGBT devices, wherein a first SiC IGBT device of thesecond pair of SiC IGBT devices is electrically connected to a secondSiC IGBT device of the second pair of SiC IGBT devices by a secondterminal, the second terminal serving as a drain of the first SiC IGBTdevice of the second pair of SiC IGBT devices and a source of the secondIGBT device of the second pair of SiC IGBT devices, a second voltageswitch, and a second feedback line. In some embodiments, the ESP VSDcontrol system further includes an offshore platform above a well,wherein the ESP assembly is downhole in the well, the VSD controller ison the offshore platform, and wherein the ESP power cable extendsbetween the VSD controller and the ESP assembly. In certain embodiments,the inverter active switch section includes three SiC powersemiconductor modules, each module packaged in a housing and including aheat sink baseplate. In some embodiments, each of the at least one SiCpower semiconductor modules includes a plurality of the pairs of SiCIGBT devices.

An illustrative embodiment of a variable speed drive (VSD) controlsystem includes a pump assembly including an induction motor operativelycoupled to a pump, a power cable and a transformer electrically coupledbetween the induction motor and a VSD controller, the VSD controllercontrolling a speed of the induction motor, the VSD controller includinga converter section that sends a direct current, the DC link including aDC smoothing capacitor that smooths the direct current, an inverteractive switch section that converts the smoothed direct current to apulse width modulated (PWM) output voltage, the inverter active switchsection including at least one silicon carbide (SiC) power semiconductormodule, and a PWM filter that filters the PWM output voltage to producenear sinusoidal voltages, the PWM filter including a plurality ofinductors, and the PWM filter sending voltage to the transformer. Insome embodiments, each of the at least one SiC power semiconductormodules includes a SiC MOSFET. In certain embodiments, each of the atleast one SiC power semiconductor modules includes at least one pair ofSiC MOSFETs. In some embodiments, each of the at least one SiC powersemiconductor modules includes a SiC IGBT device. In certainembodiments, each of the at least one SiC power semiconductor modulesincludes at least one pair of SiC IGBT devices. In some embodiments, theconverter section includes a plurality of second SiC power semiconductormodules, each of the plurality of second SiC power semiconductor modulesincluding at least one pair of SiC MOSFETs. In certain embodiments, theconverter section includes a plurality of second SiC power semiconductormodules, each of the plurality of second SiC power semiconductor modulesincluding at least one a pair of SiC IGBT devices. In some embodiments,the pump is a multi-stage centrifugal surface pump. In certainembodiments, the pump is a progressive cavity pump.

In further embodiments, features from one embodiment may be combinedwith features from any of the other embodiments. In further embodiments,additional features may be added to the specific embodiments describedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of illustrativeembodiments of the invention will be more apparent from the followingmore particular description thereof, presented in conjunction with thefollowing drawings wherein:

FIG. 1 is a schematic of an exemplary variable speed drive (VSD)controller with an inverter section of an illustrative embodiment.

FIG. 2 is a schematic of an exemplary VSD controller of an illustrativeembodiment having an active front end converter section and invertersection of an illustrative embodiment.

FIG. 3 is a schematic of an illustrative embodiment of a power andcontrol system for an electric submersible pump (ESP) motor.

FIG. 4 is a schematic diagram of an illustrative embodiment of a VSDcontrol section.

FIG. 5A is a perspective view of a VSD controller module containing twosilicon carbide power semiconductor devices of an illustrativeembodiment.

FIG. 5B is a schematic of a MOSFET type module of an illustrativeembodiment.

FIG. 5C is a schematic of an IGBT type module of an illustrativeembodiment.

FIG. 6 is a perspective view of an offshore ESP assembly powered by aVSD controller of an illustrative embodiment.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and may herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that theembodiments described herein and shown in the drawings are not intendedto limit the invention to the particular form disclosed, but on thecontrary, the intention is to cover all modifications, equivalents andalternatives to such embodiments that fall within the scope of thepresent invention as defined by the appended claims.

DETAILED DESCRIPTION

An electric submersible pump (ESP) variable speed drive (VSD) controllerwill now be described. In the following exemplary description, numerousspecific details are set forth in order to provide a more thoroughunderstanding of embodiments of the invention. It will be apparent,however, to an artisan of ordinary skill that the present invention maybe practiced without incorporating all aspects of the specific detailsdescribed herein. In other instances, specific features, quantities, ormeasurements well known to those of ordinary skill in the art have notbeen described in detail so as not to obscure the invention. Readersshould note that although examples of the invention are set forthherein, the claims, and the full scope of any equivalents, are whatdefine the metes and bounds of the invention.

As used in this specification and the appended claims, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to a powerdevice includes one or more power devices.

“Coupled” refers to either a direct connection or an indirect connection(e.g., at least one intervening connection) between one or more objectsor components. The phrase “directly attached” means a direct connectionbetween objects or components.

For ease of description and so as not to obscure the invention,illustrative embodiments are described in terms of a downhole ESP pumpassembly. However, illustrative embodiments are not so limited and maybe employed where it is desirable to decrease power loss, increaseswitching frequency and decrease footprint of a VSD, for example in VSDcontrollers for horizontal surface pumps operated by induction motorsthat may employ multi-stage centrifugal pumps, progressive cavity pumpsemploying a surface motor, and/or for electric submersible progressivecavity pumps employing a downhole ESP motor.

Illustrative embodiments provide a VSD controller for an ESP inductionmotor that employs one or more silicon carbide power semiconductordevices. The silicon carbide power semiconductor device of illustrativeembodiments replaces the conventional silicon power semiconductordevices typically used in VSD inverters employed in ESP assemblies. TheVSD controller of illustrative embodiments may increase VSD efficiencyto 98% efficiency, measured as the power out to the ESP motor versus thepower into the drive. For ESP drives 98% efficiency is a significantimprovement over the conventional 97% efficiency. Illustrativeembodiments may minimize switching losses, run at a higher switchingfrequency, and produce more power in a smaller footprint thanconventional silicon power devices employed in VSD inverters for ESPs.Silicon-based inverters for drives operating ESP motors conventionallyrun at a switching frequency less than 5 kHz. In contrast, illustrativeembodiments may provide an ESP main drive controller with a switchingfrequency greater than 20 kHz. The VSD of illustrative embodiments mayhave a smaller footprint and lower cost than conventional VSDs for ESPassemblies at the same power output. The smaller footprint may beaccomplished as a result of the increased switching frequency ofillustrative embodiments. The increased frequency may permit as much asa 10-35% decrease in the size of the PWM filter inductor footprint, theinductors being a primary contributor to footprint size.

FIG. 1 and FIG. 2 show block diagrams of illustrative embodiments of avariable speed drive controller that has a power output of between fiftyhorsepower (hp) and 3,000 hp, which may be the power requirement for anexemplary ESP motor. VSD controller 305 may be a 500 kVA drive andinclude diode bridge converter section 100, DC link 105, invertersection 110 and PWM filter section 115 sub-systems. In some embodiments,diode bridge converter section 100 may include three-phase, six-pulse,full-wave diode bridge 130, as shown in FIG. 1. In some embodiments, asshown in FIG. 2, diode bridge converter section 100 may be replaced withactive front end (AFE) converter 205. AFE converter 205 may draw currentsinusoidally to assist in reducing harmonics as compared to theembodiment of diode bridge converter section 100 of FIG. 1. In AFE 205embodiments, one or more silicon carbide (SiC) power semiconductordevices 125 may be employed in AFE 205. As shown in FIG. 2, six SiCpower devices 125 may be included in AFE 205. Also as shown in FIG. 2,LCL input filter 200 may be employed in AFE converter 205 embodiments.In the embodiments of FIG. 1 and FIG. 2, DC link 105 may includecapacitor 120 which may smooth out the DC output ripple of converter 100or AFE converter 205 and provides a stiff input to inverter section 110.As illustrated, inverter section 110 may include six SiC power devices125, although the number of SiC power devices 125 may be modified basedon system requirements. The filtered DC voltage may be converted to PWMoutput voltage using the active switching elements of SiC power devices125 of inverter section 110. These PWM signals may be filtered by PWMfilter section 115 to obtain near sinusoidal voltages. PWM filtersection 115 may include inductors 135.

FIG. 4 shows a block diagram of the control section of a firmwareimplementation of an illustrative embodiment. Since speed sensing is notan option for ESP motor 320 thousands of feet underground, and precisepositioning and speed control is not necessary, a simple volt per hertzimplementation may be employed in ESP embodiments. ESP motor 320 may bean AC, two-pole, three-phase squirrel cage induction motor operating toturn a multistage centrifugal pump. The speed of ESP motor 320 is afunction of frequency, and the speed of ESP motor 320 should be adjustedto match well productivity. If ESP motor 320 speed is not properlyadjusted, motor 320 may overheat due to a lack of cool fluid flowing byduring operation. Temperature and current feedback are sensed intransducer 400 for fault detection and shutdown. Bus voltage feedback,which is also sensed in transducer 400, is used for bus followeralgorithm 420. Offset into the sine lookup table 425 is calculated inspeed calculator 415 based on the acceleration/deceleration timesetting, demanded speed, direction of rotation of ESP motor 320, andwhether ESP motor 320 is ramping or in steady state condition. There maybe three offsets (120 degrees apart). This offset may be augmented ifthe bus voltage is pumped up during fault condition of a large inertiaload by bus follower algorithm 420. PWM waveform generator 405 then maygenerate the PWM output based on the output from sine lookup 425 and theV/Hz setting. Fault processor 410 may modify the PWM to limit thecurrent or completely shut down the output as needed.

Power devices 125 may comprise, constitute and/or include SiC powersemiconductor devices, rather than conventional silicon powersemiconductor devices. To date, although SiC power devices provide highswitching frequencies and low losses, SiC power devices have not beensuccessfully employed in ESP VSD controller systems due to unique systemrequirements and constraints facing the ESP industry. VSD controller 305may be required to power and control motor 320 thousands of feet belowthe surface of the ground in harsh downhole environments, where ambientconditions may be unknown. Speed of motor 320 must be continuously andremotely monitored and adjusted based on well productivity, fluidcomposition and ambient conditions to prevent motor overheating and/orfailure, without the benefit of speed sensing.

FIGS. 5A illustrates a perspective view of a SiC power device module ofan illustrative embodiment. One or more SiC power devices 125 maybeincluded in module 500. SiC power device 125 may be rated at between 100and 600 amperes and employed in VSD controller 305 to operate ESP motor320. SiC power device 125 may allow a VSD controller 305 with a smallerinductor footprint than conventional silicon power devices at the samepower output, although footprint may vary by manufacturer. Illustrativeembodiments of SiC power semiconductor device 125 may be obtained fromthe Wolfspeed division of Cree, Inc. of Durham, N.C., SemikronInternational Gmbh of Nuremberg, Germany or Powerex Inc. of Youngwood,Pa.

In some embodiments, SiC power device 125 may include a chip set of 3C,4H and/or 6H silicon carbide polytype crystal structure wafers, and becased in an industrial housing. In an exemplary embodiment, an all-SiCpower device 125 may include a chipset containing 1200V, 1700V or highervoltage silicon carbide metal-oxide-semiconductor field-effecttransistors (MOSFETs) and SiC diodes.

FIG. 5B illustrates a SiC MOSFET embodiment of SiC power device 125employing two SiC MOSFETs 540 per module 500. In the embodiment of FIG.5B, module 500 includes a pair of two MOSFETs 540, arranged electricallyone adjacent and/or above the other. First terminal 505 may be the drainof first MOSFET 240 and also the source of second MOSFET 240 of the pairof MOSFETs 240 in module 500 of illustrative embodiments. Secondterminal 510 may be the source of second MOSFET 240 and third terminal515 may be the drain of first MOSFET 240. First switch 520 may controlvoltage (on or off) of first MOSFET 240 and second switch 530 maycontrol voltage (on or off) of second MOSFET 240. First feedback line525 and second feedback line 535 may function as a feedback circuit forfirst and second MOSFET 240, respectively. Module 500 may include asingle MOSFET 540, a pair of MOSFETs 540 or multiple pairs of MOSFETs540.

In some embodiments, SiC power device 125 may include insulated gatebipolar transistors (IGBT) and SiC diodes, rather than MOSFETs 240. FIG.5C illustrates module 500 having IGBT type SiC power devices 125. TwoIGBT devices 560 may be included in module 500, arranged electricallyone adjacent and/or above the other. Terminals 505, 510, 515, switches520, 530 and feedback lines 525, 535 may function similarly in IGBTdevices 560 as in MOSFET 240 embodiments. Module 500 may include asingle IGBT device 560, a pair of IGBT devices 560 or multiple pairs ofIGBT devices 560.

As illustrated in FIGS. 5A-5C, module 500 includes two SiC power devices125 in a pair, either two MOSFETs 240 or two IGBT devices 260. One ormore SiC power devices 125 may be packaged in one module 500, such astwo, three, six, eight, or more. Module 500 may include housing 555 andbaseplate 545. Baseplate 545 may be copper or AlSiC, and the SiCsemiconductors may be isolated from baseplate 545 with an insulator suchas aluminum nitride or Si₃N₄. Baseplate may include openings 550 toallow baseplate to be mounted to a heat sink. One or more modules 500may form inverter section 110 and/or AFE converter 205.

FIG. 3 is a schematic of an ESP VSD controller system of illustrativeembodiments. As shown in FIG. 3, VSD controller 305 may obtain powerfrom electrical grid 300. VSD controller 305 may include invertersection 110 and/or AFE converter section 205 employing one or moresilicon carbide power devices 125, which power devices 125 may comprisesilicon carbide semiconductor power modules including silicon carbidesemiconductor chip sets such as SiC MOSFETs 240 and/or SiC IGBT devices260. VSD 305 may connect to transformer 310. Transformer 310 may step up480 volt VSD controller 305 output to the appropriate medium voltage ofESP motor 320 by selecting the correct taps on transformer 310.Transformer 310 may be slightly over designed to prevent saturation whenoperating in DC boost during startup of ESP motor 320. ESP power cable315 may extend between transformer 310 at the surface of a well, and ESPmotor 320 located downhole in the well. ESP power cable 315 may includethree insulated copper conductors that are enclosed by a helicallywrapped strip of galvanized steel armor. The galvanized steel armorstrip may be between 20 and 34 mils thick, and ESP power cable 315 mayweigh about 1.5 pounds per foot. A zinc coating may cover the surface ofthe galvanized steel armor. ESP power cable 315 may be between 4,000 and12,000 feet in length depending on well depth and/or distance from VSDcontroller 305.

FIG. 6 illustrates an ESP assembly of an illustrative embodiment. ESPassembly 600 may be placed downhole in a well, such as an oil wellunderground below the ocean. In offshore embodiments, VSD controller 305may be placed in cabinet 640 inside control room 635 on offshoreplatform 645, such as an oil rig. Power cable 315 may extend from VSDcontroller 305 and/or transformer 310 to ESP motor 320 and plug and/ortape into ESP motor 320. ESP motor 320 may be towards the bottom of ESPassembly 600, just above downhole sensors deep within a well. Powercable 315 may be up to 12,000 feet in length. ESP motor 320 may be atwo-pole, three-phase squirrel cage induction motor that operates toturn ESP pump 615. ESP pump 615 may be a multi-stage centrifugal pumpincluding impeller and diffuser stages, which ESP pump 615 may liftfluid such as oil or other hydrocarbons through production tubing 630 tostorage tanks onboard offshore platform 645. In some embodiments, pump615 may be a horizontal surface pump, progressive cavity pump or anelectric submersible progressive cavity pump. A motor seal section andintake section may extend between motor 320 and pump 615. Well casing625 may separate ESP assembly 600 from well formation 305 and/orseawater. Perforations in casing 625 may allow fluid from formation 605to enter casing 625 underground. VSD controller 305 may control andpower ESP motor 320 to adjust the speed of motor 320 to match wellproductivity.

An ESP VSD controller has been described. Illustrative embodimentsprovide an improved power system for an ESP motor employed downhole. TheSiC power device of illustrative embodiments may be a semiconductorpower device made of silicon carbide and employed in a VSD inverterand/or VSD converter. The silicon carbide power device may replace theconventional silicon power devices employed in VSD inverters used in ESPapplications. Illustrative embodiments may provide a VSD inverter withreduced switching losses, and a power output of 50 hp −3,000 hp with asmaller footprint, as compared to a silicon power device of conventionalESP power systems. The power system described herein may be employed inother types of pumps in addition to downhole ESP pumps, such as surfacepumps, progressive cavity pumps and/or electric submersible progressivecavity pumps.

Further modifications and alternative embodiments of various aspects ofthe invention may be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the scope and range of equivalents as described in thefollowing claims. In addition, it is to be understood that featuresdescribed herein independently may, in certain embodiments, be combined.

What is claimed is:
 1. A variable speed drive (VSD) control systemcomprising: a pump assembly comprising an induction motor operativelycoupled to a pump; a power cable electrically coupled between theinduction motor and a VSD controller; the VSD controller controlling aspeed of the induction motor, the VSD controller comprising: a convertersection that sends a direct current; a DC link comprising a DC smoothingcapacitor that smooths the direct current; and an inverter active switchsection that converts the smoothed direct current to a pulse widthmodulated (PWM) output voltage, the inverter active switch sectioncomprising one of at least one silicon carbide (SiC) MOSFET or at leastone SiC IGBT device.
 2. The VSD control system of claim 1, wherein theinverter active switch section comprises the at least one SiC IGBTdevice, the at least one SiC IGBT device further comprising: a first SiCIGBT device electrically connected to a second SiC IGBT device by aterminal; and the terminal serving as a drain of the first SiC IGBTdevice and a source of the second IGBT device.
 3. The VSD control systemof claim 1, wherein the inverter active switch section comprises the atleast one SiC MOSFET, the at least one SiC MOSFET further comprising: afirst SiC MOSFET electrically connected to a second SiC MOSFET by aterminal; and the terminal serving as a drain of the first SiC MOSFETand a source of the second SiC MOSFET.
 4. The VSD control system ofclaim 1, wherein the pump is a horizontal surface pump.
 5. The VSDcontrol system of claim 1, further comprising a transformer electricallycoupled between the induction motor and the VSD controller.
 6. The VSDcontrol system of claim 5, further comprising a PWM filter that filtersthe PWM output voltage to produce near sinusoidal voltages, the PWMfilter comprising a plurality of inductors, and the PWM filter sendingvoltage to the transformer.
 7. The VSD control system of claim 1,further comprising a PWM filter that filters the PWM output voltage toproduce near sinusoidal voltages.
 8. The VSD control system of claim 1,wherein the converter section comprises a three-phase, six-pulse,full-wave diode bridge.
 9. The VSD control system of claim 1, whereinthe one of the at least one SiC MOSFET or the at least one SiC IGBTdevice forms at least one SiC power semiconductor module.
 10. The VSDcontrol system of claim 9, wherein each of the at least one SiC powersemiconductor modules is packaged in a housing and comprises a heat sinkbaseplate.
 11. The VSD control system of claim 1, wherein the VSDcontroller comprises an LCL input filter and the converter sectioncomprises an active front end, the active front end comprising at leastone SiC power semiconductor module.
 12. A variable speed drive (VSD)control system comprising: a pump assembly comprising an induction motoroperatively coupled to a pump; a power cable electrically coupledbetween the induction motor and a VSD controller; the VSD controllercontrolling a speed of the induction motor, the VSD controllercomprising: a converter section that sends a direct current; a DC linkcomprising a DC smoothing capacitor that smooths the direct current; aninverter active switch section that converts the smoothed direct currentto a pulse width modulated (PWM) output voltage, the inverter activeswitch section comprising at least one silicon carbide (SiC) powersemiconductor module.
 13. The VSD control system of claim 12, whereineach of the at least one SiC power semiconductor modules comprises atleast one SiC MOSFET.
 14. The VSD control system of claim 12, furthercomprising a PWM filter that filters the PWM output voltage to producenear sinusoidal voltages, the PWM filter comprising a plurality ofinductors.
 15. The VSD control system of claim 12, wherein each of theat least one SiC power semiconductor modules comprises at least one SiCIGBT device.
 16. The VSD control system of claim 12, wherein theconverter section comprises a plurality of second SiC powersemiconductor modules, each of the plurality of second SiC powersemiconductor modules comprising at least one pair of SiC MOSFETs. 17.The VSD control system of claim 12, wherein the converter sectioncomprises a plurality of second SiC power semiconductor modules, each ofthe plurality of second SiC power semiconductor modules comprising atleast one a pair of SiC IGBT devices.
 18. The VSD control system ofclaim 12, wherein the pump is a multi-stage centrifugal surface pump.